Typical commercial aircraft include numerous windows that are distributed along both sides of the fuselage from the front of the aircraft to just before the tail. The fuselage is tubular and varies in diameter or radius between the forward and aft ends of the aircraft, and correspondingly the size and curvature of the windows can also vary along the length of the aircraft. Each window includes an outer window frame mounted in a corresponding aperture in the external skin of the aircraft, and each outer window frame supports a corresponding exterior window pane assembly. In a finished aircraft, an inner window assembly is typically mated with the outer window assembly and the inside of the external skin, and connects to interior wall panels of the aircraft.
Typical aircraft skins are made of high strength metal, such as aluminum, or, more recently, carbon fiber composite materials. The outer window assembly and the skin of the aircraft fuselage combine to form a pressure vessel, which contains the pressurized interior environment when the aircraft is at altitude. It is therefore desirable that an outer window assembly of an aircraft have sufficient mechanical strength to withstand the pressure and other mechanical loads that it will face.
To provide the desired strength, aircraft window frames have typically been made of high strength metal. Metals, however, tend to be relatively heavy, and aircraft weight directly affects aircraft efficiency during flight. Accordingly, materials, components and assemblies, including aircraft window assemblies, are being continually developed for reducing aircraft weight while providing sufficient strength of the various aircraft components. In recent years, for example, aircraft manufacturers have developed aircraft designs and fabrication methods that make greater use of composite materials, including reinforced thermoplastics such as carbon fiber reinforced plastic (“CFRP”), and carbon fiber composite materials, such as graphite/epoxy.
Reinforced thermoplastic and composite materials can be significantly lighter than traditional aircraft materials (e.g. aluminum, titanium, steel and alloys of these), while still providing high strength in a variety of aircraft applications. Reinforced thermoplastic and composite materials have been applied in various ways to aircraft window structures. Some of these, however, can be relatively complicated to fabricate and install, and present the possibility for further weight reduction. Additionally, some prior window frame assemblies can be costly, and in some cases are susceptible to cracking from fatigue and during fastener installation.
The present application seeks to address one or more of the above issues.